A gesture sensor is a human interface device that enables the detection of physical movement proximate to (but not touching) the device. The detected movement can be used, for example, as an input command for the device or for other purposes. In some applications, the device is programmed to recognize distinct non-contact hand motions, such as left-to-right, right-to-left, up-to-down, down-to-up, and in-and-out hand motions.
Generally speaking, gesture recognition enables humans to interface with devices (sometimes known as “Human Machine Interface” or “HMI”) without touching the devices. There are many possible applications for HMI based upon gesture recognition. For example, sensors have found popular use in handheld devices, such as tablet computing devices and smartphones, and other portable devices such as laptops. Gesture sensors are also being implemented in video game consoles to detect the motion of a video game player.
Most conventional gesture sensor implementations use three or more illumination sources, such as light emitting diodes (LEDs), and a light sensor, such as a photodetector. Typically, the illumination sources are turned on and off, or flashed, in succession in order for the sensor to obtain spatial information from reflection of the flashed light.
FIG. 1 illustrates a simplified block diagram of a conventional gesture sensor apparatus. A photosensor 4 is positioned proximate light emitting diodes LED 1, LED 2, and LED 3. A control circuit 5 is programmed to successively turn on and off the LEDs 1-3 and to analyze the resulting measurements sensed by the photosensor 4.
FIG. 2 illustrates an example method for detecting a moving target using the gesture sensor apparatus of FIG. 1. The motion is detected by observing the relative delay between sensed signals from the same-axis LEDs. For example, to detect left-to-right or right-to-left motion, the signals sensed by the LEDs 1 and 2 are compared. LED 1 is flashed at a different time than LED 2. That is, the LEDs 1 and 2 are positioned in known locations and are turned on and off in a known sequence. When the light from the LEDs strikes a target moving above the LEDs, light is reflected off the moving target back to the photosensor 4. The sensed reflected light is converted to a voltage signal which is sent to the control circuit 5. The control circuit 5 includes an algorithm that uses the LED positions, the LED firing sequences, and the received sensed data to determine relative movement of the target.
FIG. 2 shows, on the bottom left, the sensed voltage signals for the case of left-to-right motion. A sensed voltage signal is a voltage versus time curve. The curve labeled “Signal from LED 1” shows the sensed voltage resulting from repeated flashes of the LED 1. The low portion of the curve indicates the target is not passing over, or near, the LED 1. In other words, the target is not within the “field of view” of the photosensor 4 whereby light emitted from the LED 1 can be reflected off the target and onto the photosensor 4. If the target is not within the field of view of the photosensor 4 as related to the LED 1, the photosensor 4 does not sense any reflections of light emitted from LED 1. The high portion of the curve indicates the target is passing over, or near, the LED 1. The curve labeled “Signal from LED 2” shows the sensed voltage resulting from repeated flashes of the LED 2. While LED 1 is on, LED 2 is off, and vice versa. While the target is positioned over, or near, LED 1, the sensed voltage related to flashing of LED 1 is high, but the sensed voltage related to flashing of the LED 2 is low. While the target is positioned in the middle, between the two LEDs 1 and 2, the photosensor 4 detects reflected light from flashing of both LED 1 and LED 2. While the target is positioned over, or near, LED 2, the sensed voltage related to flashing of LED 2 is high, but the sensed voltage related to flashing of the LED 1 is low. When the target is not positioned over either LED 1 or LED 2 or between LED 1 and LED 2, the photosensor 4 does not sense reflected light associated with either and the corresponding sensed voltage levels are low.
It will therefore be appreciated that for left-to-right motion, the sensed voltage level for “signal from LED 1” goes high before the sensed voltage level for “signal from LED 2”, as shown in FIG. 2. In other words, the voltage versus time curve of “signal from LED 2” is delayed relative to the voltage versus time curve of “signal from LED 1” when the target is moving from left-to-right. For right-to-left motion, as illustrated on the bottom right portion of FIG. 2, the sensed voltage level for “signal from LED 2” goes high before the sensed voltage level for “signal from LED 1”, as shown in the two voltage versus time curves on the left hand side of FIG. 2. In other words, the voltage versus time curve of “signal from LED 1” is delayed relative to the voltage versus time curve of “signal from LED 2” when the target is moving from right-to-left.
Other motions can also be sensed with the apparatus of FIG. 1. For example, up and down motion, where up and down is considered to be motion in the y-axis, can be determined using LEDs 2 and 3 and the corresponding voltage versus time data. The control circuit 5 receives the sensed voltage from the photosensor 4 and determines relative target motion in the y-axis in a similar manner as that described above in relation to the x-axis.
A number of portable devices can benefit from the inclusion of a gesture-based HMI. There are, for example, instances where it is inconvenient, impractical or even illegal to handle a cellular telephone (a/k/a “cell phone”, “mobile phone”, “smartphone”, etc.) such that a gesture-based HMI would be very useful. For example, in some states it is not legal to hold a cell phone while driving. The same may apply to other portable devices with display screens, such as tablet computers, GPS units and laptop computers. Collectively, these devices will be referred to as “portable digital devices.”
Portable digital devices are almost universally battery powered. Since it is typically the goal to extend battery life in such devices, various battery-saving techniques are often used. For example, portable digital devices with display screens (e.g. smartphones, tablets, GPS units, laptops, etc.) can be put into sleep modes (where the display screen is typically turned off) or other a low-power states by turning off the display screens after a period of inactivity to save power and extend battery life.
Also, portable digital devices are prone to theft due to their small size and high value. For that reason, many portable digital devices have an “auto-lock” feature whereby a password or the like is required to unlock the device for use. For example, a user may be required to enter a multi-digit passcode on a touch-screen display to unlock the device.
Portable digital devices need to be awakened and/or unlocked (generically referred to herein as “activated”) when a user wishes to interact with them again. For example, with a smartphone this is typically accomplished by pressing a button, then sliding a slider bar to the right or left, and/or entering a code. All of these actions require physical contact with the smartphone, and can be inconvenient and/or dangerous tasks to be performed while, for example, driving a vehicle.
These and other limitations of the prior art will become apparent to those of skill in the art upon a reading of the following descriptions and a study of the several figures of the drawing.